What Is Happening at 43rd and Baltimore?

At the risk of quashing a blossoming and dedicated club of Mill Creek sewer infrastructure/sinkhole aficionados in West Philadelphia, we just have to say it:

It is not, technically, a sinkhole.

While most people call any hole in the street a “sinkhole,” those are natural, geological phenomena caused by limestone eroding and creating holes and caverns, or more generically, depressions where drainage collects.

And the site everyone is talking about? It isn’t actually THE infamous Mill Creek Sewer. Rather, what folks are seeing is a part of the system that feeds into what was once the creek.

Everyone OK?

Alright then, to the facts!

We are, of course, speaking of the much-covered and ogled construction site where an issue with a sewer—call it a wash-out or cave-in—eroded a copious amount of soil beneath Baltimore Avenue at 43rd Street.

That created a large gap between the road and the top of a smaller sewer that is not the Mill Creek Sewer.

“This is actually good news in some ways, considering that it would have been much worse if the actual Mill Creek sewer failed,” says our resident historian, Adam Levine. “If that had happened, it could have been a 40-foot deep hole the size of a house. We could have been out there for months and months.”

As it is, the hole that was excavated to make repairs—PWD work should be finished by the end of June—was about 12 feet deep (and 25 feet at the deepest point of excavation). Reports about a three-foot-wide hole began to come in on June 4, and the intersection was immediately closed:

An inspection revealed the large washed-out area beneath the street. With considerable help from a jackhammer-equipped backhoe, the “cavernous maw” that has since spawned everything from “Sinkhole Pizza Parties” to buttons that boast surviving “Sinkhole Summer 2019” was uncovered:

What's Next for the Neighborhood?

Once our sewer work is done, getting the intersection back open could take more time, as we coordinate with SEPTA to get the Route 34 Trolley tracks back in place. Route 34 riders can check on the status of the work in the Alerts box in the middle of SEPTA’s home page or view the current status on the SEPTA Realtime route page. (The route even has its own Twitter account.)

Residents of any neighborhood who see street or sidewalk depressions or holes in the street should report the exact location to the PWD hotline, (215) 685-6300, right away. 

The details: What happened to make this big hole?

PWD excavation revealed, among other things, a broken storm drain or inlet pipe leading to a wellhole, a vertical shaft that helps spread out pressure during high volume, wet weather days and can provide access for inspections and maintenance.
   
There was also a roughly 3.5-foot “egg-shaped” sewer. Built in 1888, its bottom layer of brick had been washed out. This smaller sewer runs east toward the Mill Creek Sewer, which is much deeper under the street and nearly 20 feet in diameter.

Here’s the difference in size:

While our inspectors do not know precisely what caused the big wash-out below the pavement, heavy afternoon rainstorms likely washed water into the broken inlet pipe. That carried off the soil-fill under the avenue this spring and further damaged the sewer.

Repairs are being completed on a manhole, the smaller sewer, and the inlet pipe that allows stormwater from the street to flow into the sewer.

In addition to the fact that no one was hurt, a silver lining can be found in the fact that this area has a less dense network of pipes, wires, gas and other infrastructure that can make repairs in places like Center City take much longer.

Currently, we don’t anticipate any water shutoffs or other utility interruptions. Here's a shot of the site on June 18 with the hole filled and the new manhole's riser section peeking up.

Mark E. Waas, a P.E. and our Director of Field Operations, has worked in the industry for over 30 years and says the incident isn’t extremely uncommon — even if the local viral news response makes it seem that way.

“It certainly is not the norm, but large cave-ins of this type do happen occasionally,” says Waas. “This one just happens to be in a very public location and impacts the trolleys, which has made it a bigger story.”

Live in the area and want updates?

Signup for PWD email/text updates and include your ZIP code and we’ll send info out to nearby residents as the project wraps up.